1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display (LCD) device implementing removable printed circuit board.
2. Discussion of the Related Art
Liquid crystal displays (LCDs) are gaining in popularity for use in systems such as television receivers, computer monitors, avionics displays, aerospace displays, and other military-related displays where the elimination of cathode ray tube (CRT) technology is desirable for several reasons. In particular, CRTs are characterized by large depth dimensions, undesirably high weight, and fragility. Additionally, CRTs require a relatively high voltage power supply to sufficiently accelerate electron beams for displaying images.
As shown in FIG. 1, a typical liquid crystal display module 100 includes a liquid crystal panel 110, a lower frame 120, an upper frame 130, and a back light unit 140. The liquid crystal panel 110 has an upper substrate, a lower substrate, and a liquid crystal layer interposed therebetween. The lower frame 120 is disposed under the liquid crystal panel 110 to support the liquid crystal panel 110, and the upper frame 130 is disposed over the liquid crystal panel 110 to press the liquid crystal panel 110, thereby fixing the liquid crystal panel 110 between the lower and upper frames 120, 130. The back light unit 140 serves as a light source to provide light rays for the liquid crystal panel 110. The lower frame 120 is usually a plastic and supports the back light unit 140 as well as the liquid crystal panel 110.
The upper substrate (not shown) of the liquid crystal panel 110 has a color filter, a black matrix, and a common electrode. The color filter colors the light rays that radiate from the back light unit 140 as the light rays pass through the liquid crystal layer of the liquid crystal panel 110. The black matrix blocks needless portions of the rays. The lower substrate (not shown) of the liquid crystal panel 110 has a switching element and a pixel electrode. A thin film transistor (TFT) is generally used as the switching electrode. Together with the common electrode of the upper substrate, the pixel electrode applies an electric field to the liquid crystal layer. The liquid crystal panel 110 further has an upper polarizer (not shown) and a lower polarizer (not shown), that are respectively formed on the upper substrate and the lower substrate.
As shown in FIG. 2, the lower frame 120 has a base plate 122 and four side walls 124 that are respectively connected with the four side edges of the base plate 122. A front side wall 124a specifically serves to support the back light unit 140 shown in FIG. 1.
FIG. 3 shows the upper frame 130 which is generally made of metal. The upper frame 130 has the shape of a rectangular doughnut, and each side edge thereof has an L-shaped section. The side edges of the upper frame 130 surround the liquid crystal panel 110, and are coupled to the lower frame 120.
Returning to FIG. 1, the back light unit 140 has a reflector 140a, a light guide 140b, a first diffusing or protecting film 140c, a first prism sheet 140d, a second prism sheet 140e, a second diffusing or protecting film 140f, and a lamp 142. The lamp 142 produces light rays such that the rays are provided to the liquid crystal panel 110.
The liquid crystal display module 100 of FIG. 1 further includes a printed circuit board (PCB, reference 150 of FIG. 4) where driving circuits are installed to drive the liquid crystal display module 100. As shown in FIG. 4, the PCB 150 is electrically connected with the liquid crystal panel 110 via a tape carrier package (TCP) 152 (usually a flexible film). A drive IC (integrated circuit) 154 is installed in the TCP 152.
Returning now to FIG. 1, a process for assembling the above-described liquid crystal display module 100 will now be explained.
At first, all the elements of the back light unit 140 are sequentially mounted on the lower frame, and the liquid crystal panel 110 is mounted on the back light unit 140. After the liquid crystal panel 110 is properly adjusted such that the lower frame 120 can support it, the upper frame 130 is aligned over the lower frame 120 and pressed on such that the liquid crystal panel 110 is fixed therebetween. At this point, the PCB 150 is bent along a rear side edge 124b (of FIG. 2) of the lower frame 120 such that it is fixed on the lower surface of the back light unit 140. Screws or double-coated tapes are usually used for fixing the PCB 150.
The above-described liquid crystal display module 100 has a disadvantage in repairing. That is to say, if defects occur in the PCB 150, the liquid crystal display module 100 must be disassembled via a complicated process to repair the PCB 150, and then reassembled after the repairing. As a result, a liquid crystal display module 100 having a defective PCB 150 is often exchanged with a new one. Further, during reassembly after repair, the screws or double-coated tapes may cause contamination in the back light unit 140, thereby resulting in deteriorated display quality.